Grout delivery

ABSTRACT

A grout delivery system for delivery of grout to a downhole location within a borehole. The grout comprising a settable mixture of first and second flowable components. The grout delivery system is adapted to be conveyed to the location within the borehole to which grout is to be delivered and to be subsequently retrieved. The delivery system comprises a delivery head, a first reservoir for receiving a charge of the first component, and a second reservoir for receiving a charge of the second component. The delivery system is operable to cause supplies of the first and second components to be conveyed to a mixing zone at the delivery head where they are mixed to form the grout and delivered into the borehole.

TECHNICAL FIELD

This invention relates to a system and method for delivery of a flowablesubstance as a mixture comprising first and second components.

The invention has been devised particularly, although not necessarilysolely, for delivery of grout into a borehole.

BACKGROUND ART

The following discussion of the background art is intended to facilitatean understanding of the present′ invention only. The discussion is notan acknowledgement or admission that any of the material referred to isor was part of the common general knowledge as at the priority date ofthe application.

Exploration diamond drilling is used in the mining industry to drillboreholes for geological surveying. Specifically, the drilling processprovides core samples for geological analysis.

Core drilling is typically conducted with a core drill comprising outerand inner tube assemblies. The inner tube assembly comprises a coreinner tube. A cutting head is attached to the outer tube assembly sothat rotational torque applied to the outer tube assembly is transmittedto the cutting head. A core is generated during the drilling operation,with the core progressively extending along the core inner tube asdrilling progresses. When a core sample is required, the core within thecore inner tube is fractured. The inner tube assembly and the fracturedcore sample contained therein are then retrieved from within the drillhole, typically by way of a retrieval cable (which is commonly referredto as a wire line) lowered down the drill hole. Once the inner tubeassembly has been brought to ground surface, the core sample can beremoved from the core inner tube and subjected to the necessaryanalysis.

In borehole drilling operations, drilling fluid (commonly referred to adrilling mud) is used for cleaning and cooling a drill bit during thedrilling process and for conveying drilling cuttings to the groundsurface.

In certain circumstances, an underground area through which the boreholeis being drilled can be unstable or otherwise vulnerable to developmentof fractures through which drilling fluid can escape. The loss ofdrilling fluid is undesirable, both in economic terms and also as it canlead to a reduction in fluid pressure within the borehole.

With a view to preventing or at least inhibiting the loss of drillingfluid, it is known to deliver grout to the vulnerable location withinthe borehole in order to seal fractures though which may otherwiseescape.

The present invention seeks to provide a system and method for deliveryof grout to a location within a borehole. However, the invention neednot be limited to such an application and may be applicable to deliveryof other flowable substances at remote locations.

SUMMARY OF INVENTION

According to a first aspect of the invention there is provides adelivery system for delivery of a flowable substance as a mixturecomprising first and second components at a location to which thedelivery system is conveyed, the delivery system comprising a deliveryhead, a first reservoir for receiving a charge of the first component, asecond reservoir for receiving a charge of the second component, andactuation means operable to cause supplies of the first and secondcomponents to be conveyed to the delivery head at which they are mixedand delivered at the location.

With this arrangement, the flowable substance comprises a fluid mixtureof the first and second components. The mixture is fluid in the sensethat it can flow for delivery to the intended location. Typically, theflowable substance is intended to harden or set once at the deliverylocation.

Preferably, the first and second reservoirs are configured as chambersof variable volume, whereby volume contraction of the chambers causesthe first and second components to be expelled therefrom and conveyed tothe delivery head.

Preferably, each variable volume chamber is defined by a piston andcylinder arrangement, with the piston being selectively moveable withinthe cylinder to effect volume variation of the chamber.

Preferably, the actuation means is responsive to fluid pressure to causevolume contraction of the chambers.

Preferably, the actuation means includes the pistons, the arrangementbeing that the pistons are responsive to fluid pressure exerted on thesides thereof opposed to the chambers to move within the respectivecylinders and thereby cause volume contraction of the chambers.

Preferably, the delivery system further comprises a control valve meansfor controlling the supply of fluid pressure to the pistons to causemovement thereof along the cylinders, the control valve means beingconfigure to allow admission of fluid under pressure in response to afluid pressure supply exceeding a prescribed level.

Typically, the fluid pressure supply comprises fluid delivered into adrill string in the borehole, the arrangement being that the deliverysystem is configured to be accommodated within the drill string andexposed to the fluid within the drill string.

Preferably, the delivery system comprises a further control valve meansfor preventing entry of fluid from borehole into the reservoirs throughthe delivery head.

Preferably, the further control valve means is disposed between thedelivery head and the reservoirs and is configured to allow fluid flowbetween the reservoirs and the delivery head upon the fluid pressure inthe reservoirs exceeding a prescribed level.

Preferably, the delivery head defines a mixing zone at which the firstand second components are brought together for mixing to form the fluidmixture. The mixing zone may comprise a mixing chamber.

Preferably the delivery head comprises a body and the mixing zone isdefined within the confines of the body.

Preferably the mixing zone is bounded by first and second faces disposedin opposed angular relation to each other and diverging outwardlytowards an outlet opening.

Preferably, the outlet opening is provided at the periphery of the body.

Preferably, the body includes a first flow path and a second flow path,the first flow path being for communication with the first reservoir andopening onto the first face, and the second flow path being forcommunication with the second reservoir and opening onto the secondface.

The invention according to the first aspect of the invention isparticularly suitable for delivery of a flowable substance in the formof grout into a borehole during the drilling process to seal anyfractures through which drilling fluid may escape from the borehole.Typically, when unstable or other ground which would be vulnerable toleakage of drilling fluid is encountered, the drilling process istemporarily halted and the delivery system according to the invention isintroduced into the borehole to deliver grout for sealing the unstableground area. Prior to introduction of the delivery system, the drillinghead retracted partially to expose the vulnerable area of ground towhich the grout is to be delivered. After the grout has been deliveredand has set, the drilling procedure is recommenced and the groutedsection of ground is drilled.

With such an arrangement, the delivery system may be conveyed to thelocation within the borehole at which the grout is to be delivered inany suitable manner. A particularly convenient arrangement for conveyingthe delivery system to the delivery location within the borehole, andalso subsequently retrieving the delivery system, is by way of a wireline system of the type well known in borehole drilling practices.

The grout constitutes a settable mixture of first and second flowablecomponents which are brought together at the time of delivery.Accordingly, it is possible to employ grouts that otherwise might not bepossible to use for sealing a borehole (particularly a borehole whichcontains water), including latex grout and urethane grout. Thearrangement is particularly suitable for grouts which are activated uponmixing of components thereof together.

The invention according to the first aspect of the invention isparticularly suitable for delivery of water-activated grout, as thegrout can be isolated from water within the borehole until such time asit is delivered whereupon it can be activated upon contact with thewater.

Typically, the first and second components of the flowable mixturecomprise different material which are mixed together and interact toprovide the flowable mixture. However, in certain applications, thefirst and second components of the flowable mixture may comprise thesame material, in which case the first and second reservoirs each holdthe same type of material.

According to a second aspect of the invention there is provides a groutdelivery system for delivery of grout comprising a settable mixture offirst and second flowable components into a borehole, the deliverysystem comprising a delivery head, a first reservoir for receiving acharge of the first component, a second reservoir for receiving a chargeof the second component, and actuation means operable to cause asupplies of the first and second components to be conveyed to thedelivery head at which they are mixed and delivered into the borehole.

The grout delivery system according to the second aspect of theinvention may have any one or more of the features referred to above ofthe delivery system according to the first embodiment

According to a third aspect of the invention there is provided a methodof delivery of a flowable substance as a flowable mixture comprisingfirst and second components, the method comprising use of a deliverysystem according to the first aspect of the invention.

According to a fourth aspect of the invention there is provided a methodof delivery of grout as a settable flowable mixture comprising first andsecond components into a borehole, the method comprising use of a groutdelivery system according to the second aspect of the invention.

According to a fifth aspect of the invention there is provided a methodof delivery of a flowable substance as a flowable mixture comprisingfirst and second components from a first location to a second locationspaced from the first location, the method comprising conveying a chargeof the first component and a charge of the second component separatedfrom each other from the first location to the second location, mixingthe first and second components to form the flowable mixture, anddischarging the flowable mixture at the second location.

According to a sixth aspect of the invention there is provided′ a methodof delivery of grout as a settable flowable mixture comprising first andsecond components into a borehole, the method comprising conveying acharge of the first component and a charge of the second componentseparated from each other into the borehole, mixing the first and secondcomponents to form the flowable mixture, and discharging the flowablemixture into the borehole.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the present invention are more fully described inthe following description of a non-limiting embodiment thereof. Thisdescription is included solely for the purposes of exemplifying thepresent invention. It should not be understood as a restriction on thebroad summary, disclosure or description of the invention as set outabove. The description will be made with reference to the accompanyingdrawings in which:

FIG. 1 is a schematic perspective view of an embodiment of a groutdelivery system according to the invention, the grout delivery systemcomprising an elongate assembly shown in an exploded condition;

FIG. 2 is a side view of, the arrangement shown in FIG. 1;

FIG. 3 is a schematic side view, on an enlarged scale, of a piston andcylinder arrangement providing reservoirs within the elongate assembly;

FIG. 4 is a fragmentary schematic perspective view of an upper sectionof the grout delivery system in an exploded condition;

FIG. 5 is a side view of the arrangement shown in FIG. 4;

FIG. 6 is a side view of the upper section of the grout delivery systemin an assembled condition;

FIG. 7 is a fragmentary schematic view illustrating a fluid flow pathwithin the upper section of the grout delivery system;

FIG. 8 is a fragmentary schematic perspective view of a lower section ofthe grout delivery system in an exploded condition;

FIG. 9 is a side view of the arrangement shown in FIG. 8;

FIG. 10 is a fragmentary schematic perspective view of the lower sectionof the grout delivery system in an assembled condition;

FIG. 11 is a fragmentary schematic sectional view of the lower sectionof the grout delivery system, illustrating in particular a one-way flowcontrol valve arrangement in a closed condition;

FIG. 12 is a view similar to FIG. 11 except that the one-way flowcontrol valve arrangement in an open condition in response for flow; and

FIG. 13 is a view similar to FIG. 12 illustrating flow paths of groutcomponents within the upper section of the grout delivery system.

The figures depict an embodiment of the invention. The embodimentillustrates certain configurations; however, it is to be appreciatedthat the invention can take the form of many configurations, as would beobvious to a person skilled in the art, whilst still embodying thepresent invention. These configurations are to be considered within thescope of this invention.

DESCRIPTION OF EMBODIMENTS

Referring to the drawings, there is shown an embodiment of a groutdelivery system 10 according to the invention for use in a core drillingoperation in a borehole survey operation. The core drilling operation isperformed with a core drill (not shown) fitted as a bottom end assemblyto a series of drill rods which together constitute a drill string. Thecore drill comprises an inner tube assembly, which includes a core tube,for core retrieval. The core drill also comprises an outer tubeassembly.

The inner tube assembly further comprises a backend assembly whichconfigured for engagement with overshot assembly attached to a wireline, as is well-known in core drilling practices. With thisarrangement, the inner tube assembly can be lowered into, and retrievedfrom, the outer tube assembly and the drill string in which the outertube assembly is incorporated.

If during the drilling operation an underground area is encounteredwhich is unstable or otherwise vulnerable to development of fracturesthrough which drilling fluid can escape, there may be a need tostabilise that area with grout in order to seal fractures against theescape of drilling fluid. The grout delivery system 10 is provided forthat purpose. The grout delivery system 10 is adapted to be conveyed tothe location within the borehole to which the grout is to be delivered,and to be subsequently retrieved, by deployment of the overshot assemblyattached to the wire line as used with the inner tube assembly.

In this embodiment, the grout delivery system 10 is adapted to deliverthe grout as a flowable substance which can set after delivery. Theflowable substance comprising a mixture of two grout components whichchemically react when mixed together to facilitate setting of the grout.The two grout components are mixed together at the location of deliverywithin the borehole and then delivered as a highly viscous fluidmixture.

The grout delivery system 10 comprises an elongate assembly 20 having abottom end 21 and a top end 23. The elongate assembly 20 is configuredfor deployment as a unit inside the drill string, with the top end 23being adapted for engagement with the overshot assembly (not shown) sothat the assembly 20 can be lowered down the drill string and hauled upthe drill string using the wire line.

The elongate assembly 20 comprises an elongate body 31 having opposedends 33, 35. A back end assembly 37 is connected to end 33 of theelongate body 31. A delivery head assembly 39 is connected to end 35 ofthe elongate body 31.

The back end assembly 37 defines the top end 23 of the elongate assembly20 and the delivery head assembly 39 defines the bottom end 21 of theelongate assembly 20.

The elongate body 31 comprises two reservoirs 43, 45 for receivingrespective charges of the two grout components. More particularly, theelongate body 31 comprises an upper end section 47, a lower end section48, and two ducts 49 which are disposed in side-by-side relation andwhich extend between the ends sections 47, 48. The end sections 47, 48each define an end face 50 onto which the ducts 49 open.

The reservoirs 43, 45 are defined within the ducts 49, as will bedescribed in more detail later. In this way, the charges of the twogrout components are isolated from each other while in the reservoirs.

In the arrangement shown, the two ducts 49 are defined by conduits 51which cooperate to provide an integrated body structure 52 inconjunction with the upper and lower end sections 47, 48.

The upper end section 47 of the elongate body 31 is configured forconnection to the back end assembly 37, and the lower end section 48 isconfigured for connection to the delivery head assembly 39, as will beexplained in more detail later. More particularly, upper end section 47comprises a threaded coupling configured as a threaded male couplingsection 53, and lower end section 48 also comprises a threaded couplingconfigured as threaded male coupling section 55. The two end sections47, 48, including the threaded male coupling sections 53, 55 are in factof similar configuration, and so the elongate body 31 can be use ineither orientation.

A piston 61 is slidably and sealingly received in each duct 49; that is,each duct 49 constitutes a cylinder 63 in which the respective piston 61is accommodated for movement back and forth therein.

Each piston 61 and cylinder 63 cooperate to define two opposed chambers65, 67 which vary in volume with movement of the piston within thecylinder. The chamber 65 will hereinafter be referred to as the bottomchamber and the chamber 67 will hereinafter be referred to as the topchamber. In FIG. 2, the pistons 61 are depicted at the top ends of thecylinders 63 and in FIG. 3 the pistons 61 are depicted further along thecylinders so as to form the bottom chambers 65 and top chambers 67 onopposed sides of the pistons.

With this arrangement, the bottom chambers 65 have outlet ends 66opening onto end face 50 of the lower end section 48 and the and the topchambers 67 have inlet ends 68 opening onto end face 50 of the upper endsection 47.

The two bottom chambers 65 communicate with the delivery head assembly39 and define the respective reservoirs 43, 45 for receiving the chargesof the two grout components. The outlet ends 66 of the bottom chambers65 define sockets 69, the purpose of which will be explained later. Withthis arrangement, the sockets 69 are disposed at the outlet ends of thereservoirs 43, 45.

The two top chambers 67 communicate with the back end assembly 37. Aswill be explained in more detail later, the back end assembly 37 isadapted to selectively admit fluid under pressure into the two topchambers 67 to exert fluid pressure onto the pistons 61 and therebydrive the pistons along their respective cylinders 63, causing volumecontraction of the two bottom chambers 65. The volume contraction ofeach bottom chamber 65 serves to expel at least part of the charge ofthe grout component contained within the respective reservoir 43, 45.

The back end assembly 37 comprises a body 71 having an upper end 73 anda lower end 75. The body 71 is of modular construction comprising aseries of body sections 72 connected one to another, including a firstintermediate body section 72 a having a side wall 76 and a secondintermediate body section 72 b.

The upper end 73 of the back end assembly 37 is adapted for engagementwith the overshot assembly (not shown), as mentioned above, so that theelongate assembly 20 can be lowered down the drill string and hauled upthe drill string using the wire line. In the arrangement illustrated,the back end assembly 37 includes a landing collar 76 and a spearpoint77 configured for engagement with the overshot assembly. The overshotassembly includes a latch head retractor mechanism releasably engagablewith the spearhead point 77.

The lower end 75 of the back end assembly 37 is adapted to be coupled tothe upper end section 47 of the elongate body 31. In the arrangementillustrated, the lower end 75 of the back end assembly 37 comprises athreaded coupling configured as threaded female coupling section 78adapted to threadingly mate with the male coupling section 53 at theupper end section 47 of the elongate body 31. The female couplingsection 78 includes a coupling cavity 79 to receive the upper endsection 47 of the elongate body 31.

As mentioned, the back end assembly 37 is adapted to selectively admitfluid under pressure into the two top chambers 67 to exert fluidpressure onto the pistons 61 and thereby drive the pistons along theirrespective cylinders 63. For this purpose, the body 71 of the back endassembly 37 includes a fluid flow path 81 extending between the exteriorof the back end assembly 37 and the coupling cavity 79. The fluid flowpath 81 is depicted by flow lines identified by reference numeral 82 inFIG. 7.

The fluid flow path 81 comprise an inlet end section 83 comprising inletports 84 incorporated in the side wall 76 of the intermediate bodysection 72 a. The fluid flow path 81 also comprises an outlet endsection 85 comprising an outlet port 86 opening onto the coupling cavity79. The fluid flow path 81 further comprises an intermediate section 87incorporating a flow control valve 89 operable to allow fluid flow alongfluid flow path 81. In the arrangement shown, the flow control valve 89is accommodated in the second intermediate section 72 b. The flowcontrol valve 89 comprises a valve seat 91 and a valve member 92 movableinto and out of sealing engagement with the valve seat in response tofluid pressure. The flow control valve 89 is closed against fluid flowwhen the valve member 92 is in sealing engagement with the valve seat 91and is open to permit fluid flow when the valve member 92 is out ofsealing engagement with the valve seat The valve member 92 comprises avalve body 93 which guidingly received and supported within the bodysection 72 b for reciprocatory movement into and out of sealingengagement with the valve seat 91. The valve member 92 is biased intosealing engagement with the valve seat 91 by a valve spring 94 andpresents a valve face 95 which is exposed to fluid pressure, whereby thevalve member is caused to move out of sealing engagement with the valveseat 91 when the fluid pressure rises to a level which can overcome thebiasing influence of the valve spring 94. The valve body 93 incorporatesbypass ports 96 through which fluid can flow to pass around and throughthe valve body and proceed towards the outlet port 86 when the flowcontrol valve 89 is open.

With this arrangement, the flow control valve 89 is configure to allowfluid flow along the fluid flow path 81 into the coupling cavity 79, andthereby admission of fluid under pressure into the two top chambers 67which are in communication with the coupling cavity 79, in response to afluid pressure supply exceeding a prescribed level. In this embodiment,the flow control valve 89 is responsive to a fluid supply pressureexceeding 100 psi; that is, the valve is caused to open to allow fluidflow along the fluid flow path 81 when the fluid pressure on the intakeside of the valve exceeds 100 psi. It will, of course, be understoodthat the prescribed pressure can be selected at any appropriate leveland need not be limited to 100 psi.

In this embodiment, the source which is used to supply fluid pressure toactuate the grout delivery system 10 comprises water which is pumpedinto the drill string. With this arrangement, water under pressure flowsinto the back end assembly 37 and into the entry side of the flow path81. If the water pressure exceeds the prescribed level (which in thisembodiment is 100 psi), the pressure-responsive control valve means iscaused to open and thereby allow water flow along the fluid path 81 andinto the two top chambers 67. The resultant water pressure exerted ontothe pistons 61 moves the pistons along their respective cylinders 63,causing volume contraction of the two bottom chambers 65.

The delivery head assembly 39 comprises a valve assembly 101 and adelivery nozzle 103.

The valve assembly 101 is adapted to prevent entry of water fromborehole into the two reservoirs 43, 45. By way of explanation, it isoften the case that a borehole being drilled contains water throughwhich the grout delivery system 10 needs to descend as it moves to thelocation at which the grout is to be delivered. In certaincircumstances, it is important that there be no water ingress into thetwo reservoirs 43, 45 while the grout delivery system 10 is immersed inthe water. It can be particularly important that there be no wateringress in circumstances where the reservoirs 43, 45 contain awater-activated grout material.

In the absence of the valve assembly 101, the grout delivery system 10could possibly be vulnerable to ingress of water into the reservoirs 43,45, particularly during the descent in water within the borehole owingto the forces likely to be exerted on it during the descent.

The valve assembly 101 comprises a valve body 105 incorporating two flowpassages 107, each adapted to communicate with a respective one of thereservoirs 43, 45. More particularly, the flow passages 107 have inletends 109 configured as spigots 111 adapted to be sealingly received inthe corresponding socket 69 at the outlet ends of the reservoirs 43, 45.Further, the flow passages 107 have outlet ends 113 configured assockets 115 for connection to the delivery nozzle 103, as will beexplained later.

The valve body 105 accommodates a further control valve means 116comprising two one-way valves spring-loaded disc valves 117 eachassociated with one of the flow passages 107.

The two spring-loaded disc valves 117 are effectively one-way valves,allowing grout material to be dispensed from the reservoirs 43, 45 inthe manner described previously but inhibiting flow of water in thereverse direction from the borehole into the reservoirs. In thisembodiment, the two spring-loaded disc valves 117 are set to open inresponse to a prescribed pressure exerted by the grout componentmaterial as it is expelled from its respective reservoir 43, 45. Theprescribed pressure for opening of each spring-loaded disc valves 117 is10 psi in this embodiment. It will, of course, be understood that theprescribed pressure can be selected at any appropriate level and neednot be limited to 10 psi. The two spring-loaded disc valves 117 areshown in a closed condition in FIG. 11 and in an open condition in FIG.12.

The delivery nozzle 103 comprises a nozzle body 121 having an inner end123 and an outer end 125.

The nozzle body 121 comprises a threaded coupling at the inner end 123configured as threaded female coupling section 124 adapted tothreadingly mate with the male coupling section 55 at the lower endsection 48 of the elongate body 31. The female coupling section 124includes a coupling cavity 126 to receive the upper end section 47 ofthe elongate body 31.

The nozzle body 121 further comprises a cavity 128 contiguous with thecoupling cavity 126 for accommodating the valve body 105.

The nozzle body 121 further comprises a mixing zone 127 adjacent theouter end 125 at which the two grout component materials emanating fromthe reservoirs 43, 45 are brought together for mixing to form the groutfor delivery as a highly viscous fluid mixture.

The nozzle body 121 incorporates two flow passages 129, each adapted tocommunicate at one end with a respective one of the flow passages 107 inthe valve assembly 101 and to communicate at the other end with themixing zone 127. More particularly, each flow passage 129 has an inletend 131 configured as a spigot 133 adapted to be sealingly received inthe corresponding sockets 115 at the outlet ends 113 of the flowpassages 107 in the valve assembly 101. The spigots 133 extend into thecavity 128 in which the valve body 121 is accommodated. Further, eachflow passage 129 has an outlet end 135 opening onto the mixing zone 127.

In the arrangement shown, each flow passage 129 is defined by firstsection 136 communicating with the inlet end 131, a second section 137communicating with the outlet end 135, and an intervening third section138 accommodating a reduction in the cross-section flow area from thefirst section 136 to the second section 137. In the arrangement shown,the outlet end 135 is configured as an array of outlet ports 139, andeach second section 137 comprising a plurality of flow galleries (notshown) extending to the mixing zone 127 and opening onto the mixing zonevia the array of outlet ports.

The mixing zone 127 is defined within the confines of the body 121 andis bounded by first and second faces 141, 142 disposed in opposedangular relation to each other and diverging outwardly towards an outletopening 137 through which the grout is discharged into the borehole. Theoutlet ends 135 of the flow passages 129 open onto the first and secondfaces 141, 142. With this arrangement, the mixing zone 127 comprises amixing chamber 143 defined between the first and second faces 141, 142.The mixing chamber 143 is open and thereby also defines an outlet 145through which the grout can be discharged.

The angular relationship between the trajectories of the streams ofgrout component materials issuing from the outlet ports 139 into themixing zone 127 facilities mixing of the grout component materials toform the grout before discharge of the grout as a viscous fluid mixturefrom the mixing zone 127 adjacent the outer end 125. In particular, thestreams of grout component materials issuing from the outlet ports 139intersect within the mixing zone 127 to create shear which enhancesmixing efficiency.

In operation, the reservoirs 43, 45 are charged with the grout componentmaterials by loading through the lower end section 48 of the elongatebody 31. The delivery head assembly 39 is then installed in position onthe elongate body 31.

When a section of the borehole being drilled required grouting, thedrilling string is partially retracted to expose the area to be grouted,and the loaded grout delivery system 10 is lowered down the drill stringusing the overshot assembly (not shown) attached to the wire line.During the descent of the loaded grout delivery system 10, the twospring-loaded disc valves 107 function to prevent the ingress of anywater within the borehole into the reservoirs 43, 45 as previouslyexplained. When the loaded grout delivery system 10 is at the desiredlocation, water is pumped into the drill string and pressurised. Thepressurised water flows into the back end assembly 37 and into the entryside of the flow path 81. Once the water pressure exceeds the prescribedlevel (which in this embodiment is 100 psi), the pressure-responsiveflow control valve 89 is caused to open and thereby allow water to flowalong the fluid path 81 and into the two top chambers 67. The resultantfluid pressure exerted onto the pistons 61 moves the pistons along theirrespective cylinders 63, causing volume contraction of the two bottomchambers 65. This expels grout component material from the reservoirs43, 45 and causes the expelled material to flow along the respectiveflow passages 107 in the valve assembly 101. The respective flows ofexpelled material exert pressure on the two spring-loaded disc valves107 which open when the pressure exceeds the prescribed level (which is10 psi in this embodiment). The respective flows of expelled materialenter the nozzle body 121 and pass along the flow passage 129 to themixing zone 127. The flows of expelled material enter the mixing zone127 and mix to react chemically to form the grout. The flow path of theexpelled material is depicted in FIG. 13 by flow lines identified byreference numeral 147. The grout so formed is depicted schematically inFIG. 13 and identified by reference numeral 150. As alluded to above,the flows of expelled material emerging from the outlet ports 139intersect in the mixing zone 127 to create shear which enhances mixingefficiency. The resultant grout 150 is discharged as a viscous fluidmixture through the outlet 145 defined at the outer end 125 of thenozzle body 121 and delivered into the borehole. At the completion ofthe grout delivery process, the delivery of pressurized water into theborehole is terminated and the grout delivery system 10 retrieved byraising it to the ground surface using the using the overshot assembly(not shown) attached to the wire line.

From the foregoing, it is evident that the present embodiments provide asystem and method for delivering grout component materials to a locationwithin a bore hole, at which the grout component materials are mixedtogether to form the grout and deliver the grout as a flowable substancewhich can set after delivery. It is a particular feature of theembodiment that the grout components are mixed together at the locationof delivery within the borehole and then delivered into the borehole.

In the embodiments described, the two reservoirs 43, 45 were describedas being used to contain charges of two grout component materials whichreact chemically to form the grout. The two reservoirs 43, 45 may, ofcourse contain other types of grout materials.

Further, the two reservoirs may in fact be charged with the same type ofmaterial. With this arrangement, the two reservoirs would simply provideincreased holding capacity for that material.

Further, the delivery system may comprise more than two reservoirs tofacilitate mixing of more than two components to form the flowablesubstance to be delivered.

It should be appreciated that the scope of the invention is not limitedto the scope of the embodiment described.

In another embodiment, which is not shown, the nozzle body 121 maycomprise first portion configured as a disposal unit and a secondportion configured as a retaining member (such as a bezel or othermount) to releasably secure the first portion to the valve assembly 101.In this embodiment, the mixing chamber may be defined by a zone withinthe first portion. With this arrangement, the first portion can bediscarded after use and thereby avoid the need for cleaning after use.

While the embodiment has have been described with particular referenceto delivery of grout into a borehole, it should be understood that theinvention need not necessarily be limited to that application. Theinvention may be applicable to delivery of other flowable substancesinto boreholes or to other remote locations. By way of example, theinvention may find application in the delivery of flowable substancesinto a distant section of pipeline which is not otherwise readilyaccessible for the purpose of repairing or blocking that section ofpipeline.

Modifications and improvements may be made without departing from thescope of the invention.

Reference to positional descriptions, such as lower and upper, are to betaken in context of the embodiments depicted in the figures, and are notto be taken as limiting the invention to the literal interpretation ofthe term but rather as would be understood by the skilled addressee.

Throughout this specification, unless the context requires otherwise,the word “comprise” or variations such as “comprises” or “comprising”,will be understood to imply the inclusion of a stated integer or groupof integers but not the exclusion of any other integer or group ofintegers.

1. A delivery system for delivery of a flowable substance as a mixtureof first and second flowable components to a downhole location within aborehole, the delivery system being configured to be accommodated withina drill string located in the borehole and exposed to fluid within thedrill string, the delivery system comprising a delivery head, a firstreservoir for receiving a charge of the first flowable component, asecond reservoir for receiving a charge of the second flowablecomponent, and actuation means operable to cause a supplies of the firstand second flowable components to be conveyed to the delivery head atwhich they are mixed and delivered into the borehole, the actuationmeans being responsive to fluid pressure arising in use from fluiddelivered into the drill string in the borehole, a control valve meansfor controlling the supply of fluid pressure to the actuation means, thecontrol valve means being operable to allow admission of fluid underpressure in response to a fluid pressure supply exceeding a prescribedlevel, and a further control valve means for preventing entry of fluidfrom borehole into the reservoirs through the delivery head, the furthercontrol valve means being disposed between the delivery head and thereservoirs and operable to allow fluid flow between the reservoirs andthe delivery head upon the fluid pressure in the reservoirs exceeding aprescribed level.
 2. The delivery system according to claim 1 whereinthe first and second reservoirs are configured as chambers of variablevolume, whereby volume contraction of the chambers causes the first andsecond components to be expelled therefrom and conveyed to the deliveryhead.
 3. The delivery system according to claim 2 wherein each variablevolume chamber is defined by a piston and cylinder arrangement, with thepiston being selectively moveable within the cylinder to effect volumevariation of the chamber.
 4. The delivery system according to claim 3wherein the actuation means is responsive to fluid pressure to causevolume contraction of the chambers.
 5. The delivery system according toclaim 4 wherein the actuation means comprises the pistons, thearrangement being that the pistons are responsive to fluid pressureexerted on the sides thereof opposed to the chambers to move within therespective cylinders and thereby cause volume contraction of thechambers.
 6. (canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled) 10.The delivery system according to claim 1 wherein the delivery headdefines a mixing zone at which the first and second components arebrought together for mixing to form a flowable fluid mixture.
 11. Thedelivery system according to claim 10 wherein the mixing zone comprisesa mixing chamber.
 12. The delivery system according to claim 11 whereinthe delivery head comprises a body and the mixing zone is defined withinthe confines of the body.
 13. (canceled)
 14. (canceled)
 15. (canceled)16. A grout delivery system for delivery of grout comprising a settablemixture of first and second flowable grout components into a borehole,wherein the grout delivery system comprises a delivery system accordingto claim 1, and wherein the first and second flowable grout componentscomprise said first and second flowable components.
 17. (canceled)
 18. Amethod of delivery of a flowable substance as a flowable mixturecomprising first and second flowable components, the method comprisinguse of a delivery system according to claim
 1. 19. A method of deliveryof grout as a settable flowable mixture comprising first and secondcomponents into a borehole, wherein the method comprising use of a groutdelivery system according to claim
 16. 20. A method of delivery of aflowable substance as a flowable mixture comprising first and secondcomponents, the method comprising conveying a charge of the firstcomponent and a charge of the second component separated from each otherfrom a first location to a second location at the downhole location,mixing the first and second components at the second location to formthe flowable mixture, and discharging the flowable mixture into theborehole.
 21. The method according to claim 20 wherein the flowablesubstance comprises a settable mixture of first and second groutcomponents and wherein the first component comprises the first groutcomponent and the second component comprises the second grout component.22. (canceled)
 23. A grout delivery system for delivery of groutcomprising a settable mixture of first and second flowable components toa downhole location within a borehole, the delivery system beingconfigured to be accommodated within a drill string located in theborehole and exposed to fluid within the drill string, the deliverysystem comprising a delivery head, a first reservoir for receiving acharge of the first flowable component, a second reservoir for receivinga charge of the second flowable component, and actuation means operableto cause a supplies of the first and second flowable components to beconveyed to the delivery head at which they are mixed and delivered intothe borehole, the actuation means being responsive to fluid pressurearising in use from fluid delivered into the drill string in theborehole, a control valve means for controlling the supply of fluidpressure to the actuation means, the control valve means being operableto allow admission of fluid under pressure in response to a fluidpressure supply exceeding a prescribed level, and a further controlvalve means for preventing entry of fluid from borehole into thereservoirs through the delivery head, the further control valve meansbeing disposed between the delivery head and the reservoirs and operableto allow fluid flow between the reservoirs and the delivery head uponthe fluid pressure in the reservoirs exceeding a prescribed level. 24.(canceled)
 25. The delivery system according to claim 5 wherein thecontrol valve means for controlling the supply of fluid pressure to theactuation means is incorporated in a fluid flow path comprising an inletend section configured for exposure to fluid within the drill string andan outlet section configured for communication with pistons to exertfluid pressure thereon upon opening of control valve means.
 26. Thedelivery system according to claim 25 wherein the control valve meanscomprises a valve seat and a valve member movable into and out ofsealing engagement with the valve seat in response to the fluid pressuresupply exceeding said prescribed level.